Novel structuring technique for diamond coatings

Coating thickness and interlayer effects on CVD-diamond film adhesion to cobalt-cemented tungsten carbides

Effect of pretreatment strategy on the microstructure, mechanical properties and cutting performance of diamond coated hardmetal tools using HFCVD method

Growth and characterization of integrated nano- and microcrystalline dual layer composite diamond coatings on WC–Co substrates

Silicon-On-Diamond layer integration by wafer bonding technology

Tribological and mechanical properties of HFCVD diamond-coated WC-Co substrates with different Cr interlayers

It is known that in the condition of chemical vapor deposition (CVD) diamond process, molybdenum is capable of forming carbide known as the "glue" which promotes growth of the CVD diamond, and aids its adhesion by (partial) relief of stresses at the interface. Furthermore, the WC grains are reaction bonded to the Mo 2 C phase. Therefore, molybdenum is a good candidate material for the intermediate layer between WC–Co substrates and diamond coatings. A molybdenum intermediate layer of 1–3 μm thickness was magnetron sputter-deposited on WC/Co alloy prior to the deposition of diamond coatings. Diamond films were deposited by hot filament chemical vapor deposition (HFCVD). The chemical quality, morphology, and crystal structure of the molybdenum intermediate layer and the diamond coatings were characterized by means of SEM, EDX, XRD and Raman spectroscopy. It was found that the continuous Mo intermediate layer emerged in spherical shapes and had grain sizes of 0.5–1.5 μm after 30 min sputter deposition. The diamond grain growth rate was slightly slower as compared with that of uncoated Mo layer on the WC–Co substrate. The morphologies of the diamond films on the WC–Co substrate varied with the amount of Mo and Co on the substrate. The Mo intermediate layer was effective to act as a buffer layer for both Co diffusion and diamond growth.

A great deal of attention has been paid to friction and wear caused by current-carrying friction. In this study, diamond coatings were deposited on the cemented carbides (WC-Co) substrate by hot filament chemical vapor deposition method. Although the diamond coating possessed a higher roughness than the WC-Co substrate, it was effective at reducing the friction coefficient and improving the effectiveness of WC-Co in the current-carrying friction process. In the presence of 1 A, the diamond coating exhibited a lower friction coefficient than the WC-Co matrix, and the diamond transformed into graphite as a result. The results show that diamond-coated surfaces have a better wear condition than WC-Co.

Laboratory fretting testing is an appropriate method to investigate the friction and wear behaviors of hard coating materials in vibrating contacts under specified conditions. Such testing can help to select the most suitable coating for a specific application. Furthermore, it can assist in optimizing the coating deposition process. A conceptual framework for modeling laboratory fretting testing is presented together with test equipment and experimental methods for on-line mechanical analysis and off-line material degradation analysis. The application of these concepts is demonstrated for two hard coating types, namely, physical vapor deposition (PVD) TiN and chemical vapor deposition (CVD) diamond coatings. The influence of the fretting conditions on the mechanical contact response as well as on the materials modification induced in the contact is analyzed. The effect of third bodies, tribochemical reactions, and residual stress on the friction and wear behavior of these hard coatings is discussed.

The undoped and B-doped polycrystalline diamond thin film was synthesized by hot filament chemical vapor deposition and microwave plasma, respectively. The structural characterization was performed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The electrical properties of synthesized diamond layer were characterized by dc-conductivity method and charge deep level transient spectroscopy. The B-doped diamond layers show higher sp2/sp3 ratios in comparison with that of undoped layers what can have an essential influence on the localized density of states associated with shallow hydrogen acceptor states what is reflected in the values of activation energies which reached the values of 38 meV for B-doped and 55 meV for undoped diamond layers, respectively. The existence of deep level traps, as, for example, associated with B-related acceptors, was not observed.

In this paper, a 2mm-long linear on-chip dipole antenna pair on Si substrate is analyzed and simulated to investigate the transmission characteristics using Ansoft's HFSS. By inserting a 0.35mm thick diamond layer between substrate and heat sink, the obtained transmission gain of antenna pair with 1mm separation on 10 Ohm-cm Si substrate increases by 9dB at 20GHz. The effect of the dielectric materials, diamond thickness, substrate resistivity and the separation of an antenna pair on the transmission gain has been investigated. The results indicate that thinner diamond layer along with high resistivity substrate is preferred. A modified propagation model involving a diamond layer is also evaluated to make antenna performance predictable in real wireless interconnection systems.

Diamond/β-SiC composite films and diamond film with composite interlayers were synthesized on cemented carbide substrates and hard metal cutting tools. Diamond top layers and the interlayers were deposited in one single process by hot filament chemical vapor deposition (HFCVD) technique using a gas mixture of hydrogen, methane and tetramethylsilane (TMS). Two different kinds of interlayers have been employed, namely, gradient interlayer and interlayer with constant composition. The gradient composite film, featuring a cross-sectional gradient with increasing diamond/β-SiC content from film-substrate interface to the top of the film, showed the best film adhesion. Turning test was carried out using diamond coated and uncoated cutting tools to machine aluminum alloy. It was confirmed that the diamond films with gradient interlayer showed best adhesion to the hard metal cutting tools. Diamond coated cutting tool with gradient composite interlayer showed also higher wear resistance than uncoated cutting tool. The tool lifetime of such diamond coated cutting tool was 10 times higher than that of uncoated cutting tool. Moreover, diamond coated cutting tools performed non-sticking machining, which leaded to much higher surface quality of machined surface than uncoated insert.

The diamond coating of tungsten carbide (WC)–cobalt (Co) hard metals has been the focus of various research activities mainly due to growing interest in diamond-coated tools for industrial machining of different materials. In this work, multilayered diamond coatings have been grown on pretreated tungsten carbide–cobalt substrates by hot-filament chemical vapor deposition. Two types of multilayer coatings have been prepared: (a) three-layer (alternating nanocrystalline diamond and microcrystalline diamond films) and (b) five-layer (alternating ultrananocrystalline and microcrystalline diamond films). The morphology, roughness, structure, thickness, adhesion of these coatings have been investigated using atomic force microscopy, field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, nanoindentantion and Rockwell C indentation tests at 600 N load. Raman spectra of the two types of samples exhibited sharp characteristic bands of nanocrystalline diamond and a centered peak at 1340 cm−1. The displacement of this peak in relation to the natural diamond peak (1332 cm−1) can be attributed to graphitic inclusions in diamond grain boundaries and the thermal coefficient mismatch of the multilayer coating–substrate system. Roughness surface measurements showed very smooth surfaces for both samples. Although the substrate has a high binder content, the results show that well-adhered chemical vapor deposition diamond multilayer coatings were produced.

Diamond icosahedron on a TiN-coated steel substrate

Diamond coating of steel at high temperatures in hot filament chemical vapour deposition (HFCVD) employing chromium interlayers

Insulating diamond coatings on tungsten electrodes